The morphological diversity of comet 67P/Churyumov-Gerasimenko

Images of comet 67P/Churyumov-Gerasimenko acquired by the OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) imaging system onboard the European Space Agency's Rosetta spacecraft at scales of better than 0.8 meter per pixel show a wide variety of different structures and textures. The data show the importance of airfall, surface dust transport, mass wasting, and insolation weathering for cometary surface evolution, and they offer some support for subsurface fluidization models and mass loss through the ejection of large chunks of material.

Large heterogeneities in comet 67P as revealed by active pits from sinkhole collapse

Pits have been observed on many cometary nuclei mapped by spacecraft(1-4). It has been argued that cometary pits are a signature of endogenic activity, rather than impact craters such as those on planetary and asteroid surfaces. Impact experiments(5,6) andmodels(7,8) cannot reproduce the shapes of most of the observed cometary pits, and the predicted collision rates imply that few of the pits are related to impacts(8,9). Alternative mechanisms like explosive activity(10) have been suggested, but the driving process remains unknown. Here we report that pits on comet 67P/Churyumov-Gerasimenko are active, and probably created by a sinkhole process, possibly accompanied by outbursts. We argue that after formation, pits expand slowly in diameter, owing to sublimation-driven retreat of the walls. Therefore, pits characterize how eroded the surface is: a fresh cometary surface will have a ragged structure with many pits, while an evolved surface will look smoother. The size and spatial distribution of pits imply that large heterogeneities exist in the physical, structural or compositional properties of the first few hundred metres below the current nucleus surface.

Leroy-Beaulieu über die europäische Einwanderung nach Amerika

Henri Jean Baptiste Anatole Leroy-Beaulieu

Na 50 Nachlass Arthur Schopenhauer - 'Schopenhauer-Archiv', 77 - Antwort auf die Briefe vom 18. Juni und 15. Juli 1800

u.a.: Deutschlandreise; Empfehlung eines Theaterstücks von Molière;

Na 50 Nachlass Arthur Schopenhauer - 'Schopenhauer-Archiv', 38 - Replik auf die gegen ihn erhobene Kritik einer falschen Darstellung der Ethik Schopenhauers

u.a.: Kritik an der "Die beiden Grundprobleme der Ethik: Ueber die Freiheit des menschlichen Willens; Ueber das Fundament der Moral"; Auseinandersetzung mit der Ethik von Jean-Baptiste Antoine Monet de Lamarck; Erfahrungen in England mit Animal-Magnetism und Phrenologie; Corpus Iuris Civilis; Kritik an der Parerga und Paralipomena; Kapitalismuskritik; Auseinandersetzung mit dem Prinzip des Individuums in "Die Welt als Wille und Vorstellung"; Grenzen des Egoismus, Kastendenken im Buddhismus; Definition von Erscheinung; Christentum; Auseinandersetzung mit der "Kritik der reinen Vernunft" von Immanuel Kant; Das Ding an Sich; Definition von Naturzusammenhang; Willensphilosophie; Bezug auf die "Deutsche Grammatik" von Jacob Grimm; Vergleich mit Baruch Spinoza; Naturwissenschaft; Rezeption der Philosophie von Angelus Silesius; Vorhaben einer eigenen kritischen Publikation zur Ethik Schopenhauers; Sexualität; Lebensverneinung; Praxis der Hegelianer und Herbatianer; Friedrich Schelling; Platon; Silesius;

L' art de péter : essay théori-physique et méthodique

[Pierre Thomas Nicolas Hurtaut]

Composition of aerosols collected in the Western Russian Arctic in August-September 1991

In August-September 1991 during the SPASIBA expedition (Scientific Program on the Arctic and Siberian Aquatorium) aboard R/V Yakov Smirnitzky in the Laptev Sea ten samples of aerosols were collected by nylon nets. A combined approach including various analytical techniques, such as single-particle analysis, instrumental neutron activation analysis, and atomic absorption spectrophotometry, was used to study composition of the samples. Mass concentration of coarse-grained (>0.001 mm) insoluble fraction of aerosols ranged from 80 to 460 ng/m**3. In all the samples remains of land vegetation were found to be the dominant component. Organic carbon content of the aerosols ranged from 23 to 49%. Inorganic part of the samples was represented mainly by alumosilicates and quartz. Anthropogenic ''fly ash'' particles were observed in all the samples. Temporal variations of element concentrations resulted from differences in air masses entering the studied area.